Kink propagation in a two-dimensional curved Josephson junction

We consider the propagation of sine-Gordon kinks in a planar curved strip as a model of nonlinear wave propagation in curved wave guides. The homogeneous Neumann transverse boundary conditions, in the curvilinear coordinates, allow to assume a homogeneous kink solution. Using a simple collective variable approach based on the kink coordinate, we show that curved regions act as potential barriers for the wave and determine the threshold velocity for the kink to cross. The analysis is confirmed by numerical solution of the 2D sine-Gordon equation.Comment: 8 pages, 4 figures (2 in color

Dificultades para codificar, relacionar y categorizar problemas verbales algebraicos: dos estudios con estudiantes de secundaria y profesores en formación

En resolución de problemas verbales por transferencia, la activación de problemas ya conocidos que sirvan de guía, depende de las analogías percibidas entre éstos y el problema a resolver. Se desarrollan dos estudios relacionados para analizar en qué características se basan los estudiantes para codificar problemas y detectar sus analogías, en tareas de categorización (sorting). Se utilizaron técnicas cuantitativas y cualitativas combinadas. Primero se analizó cómo los estudiantes de secundaria son influidos por diferentes variables características de problemas de ciencias. Una gran proporción de sujetos no fue capaz de percibir las analogías y diferencias adecuadas entre problemas. El segundo estudio trató de avanzar una explicación de estos resultados. El nivel académico y la familiaridad con las temáticas fueron factores significativos, pero los futuros profesores participantes mostraron demasiadas dificultades, alertando sobre la conveniencia de revisar algunos supuestos instruccionales habituales

Age Discrimination in the Labour Market and Policy Responses: The Situation in the United Kingdom*

This article discusses recent research into British employers' attitudes and behaviour towards older workers and puts this in the context of developments in public policies towards older workers over the last decade. Research points to discrimination against older workers in most aspects of firm behaviour, even though when asked, managers in various studies also highlight positive attributes of older workers. Despite a recent proliferation of U.K. research in this area, it is difficult to gauge the extent of direct and indirect discrimination amongst older workers. Moreover, methodological differences make comparisons between studies problematic and it is difficult to examine trends in attitudes and behaviour. Regarding public policy, until recently policymakers focused on awareness raising campaigns among employers. While there is some evidence of increasing awareness of the issue, there is little evidence that the actual practices of employers are changing. Significant change can only be a long-term goal and would require going beyond national awareness-raising campaigns to working directly with sector bodies, trade unions and individual firms. It will also require integrated policymaking, something that the U.K. government appears to be working towards. The Geneva Papers on Risk and Insurance (2003) 28, 612–624. doi:10.1111/1468-0440.00249